Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 344f4ec4 authored by Patrick Bellasi's avatar Patrick Bellasi Committed by Leo Yan
Browse files

sched/tune: add sysctl interface to define a boost value 



The current (CFS) scheduler implementation does not allow "to boost"
tasks performance by running them at a higher OPP compared to the
minimum required to meet their workload demands.

To support tasks performance boosting the scheduler should provide a
"knob" which allows to tune how much the system is going to be optimised
for energy efficiency vs performance.

This patch is the first of a series which provides a simple interface to
define a tuning knob. One system-wide "boost" tunable is exposed via:
  /proc/sys/kernel/sched_cfs_boost
which can be configured in the range [0..100], to define a percentage
where:
  - 0%   boost requires to operate in "standard" mode by scheduling
         tasks at the minimum capacities required by the workload demand
  - 100% boost requires to push at maximum the task performances,
         "regardless" of the incurred energy consumption

A boost value in between these two boundaries is used to bias the
power/performance trade-off, the higher the boost value the more the
scheduler is biased toward performance boosting instead of energy
efficiency.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarPatrick Bellasi <patrick.bellasi@arm.com>
parent 8aaf022d

include/linux/sched/sysctl.h

+16 −0
Original line number Diff line number Diff line
@@ -77,6 +77,22 @@ extern int sysctl_sched_rt_runtime; 
extern unsigned int sysctl_sched_cfs_bandwidth_slice;

#endif



#ifdef CONFIG_SCHED_TUNE

extern unsigned int sysctl_sched_cfs_boost;

int sysctl_sched_cfs_boost_handler(struct ctl_table *table, int write,

				   void __user *buffer, size_t *length,

				   loff_t *ppos);

static inline unsigned int get_sysctl_sched_cfs_boost(void)

{

	return sysctl_sched_cfs_boost;

}

#else

static inline unsigned int get_sysctl_sched_cfs_boost(void)

{

	return 0;

}

#endif



#ifdef CONFIG_SCHED_AUTOGROUP

extern unsigned int sysctl_sched_autogroup_enabled;

#endif

init/Kconfig

+26 −0
Original line number Diff line number Diff line
@@ -1237,6 +1237,32 @@ config SCHED_AUTOGROUP 
	  desktop applications.  Task group autogeneration is currently based

	  upon task session.



config SCHED_TUNE

	bool "Boosting for CFS tasks (EXPERIMENTAL)"

	help

	  This option enables the system-wide support for task boosting.

	  When this support is enabled a new sysctl interface is exposed to

	  userspace via:

	     /proc/sys/kernel/sched_cfs_boost

	  which allows to set a system-wide boost value in range [0..100].



	  The currently boosting strategy is implemented in such a way that:

	  - a 0% boost value requires to operate in "standard" mode by

	    scheduling all tasks at the minimum capacities required by their

	    workload demand

	  - a 100% boost value requires to push at maximum the task

	    performances, "regardless" of the incurred energy consumption



	  A boost value in between these two boundaries is used to bias the

	  power/performance trade-off, the higher the boost value the more the

	  scheduler is biased toward performance boosting instead of energy

	  efficiency.



	  Since this support exposes a single system-wide knob, the specified

	  boost value is applied to all (CFS) tasks in the system.



	  If unsure, say N.



config SYSFS_DEPRECATED

	bool "Enable deprecated sysfs features to support old userspace tools"

	depends on SYSFS

kernel/sched/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -18,5 +18,6 @@ obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o 
obj-$(CONFIG_SCHED_AUTOGROUP) += auto_group.o

obj-$(CONFIG_SCHEDSTATS) += stats.o

obj-$(CONFIG_SCHED_DEBUG) += debug.o

obj-$(CONFIG_SCHED_TUNE) += tune.o

obj-$(CONFIG_CGROUP_CPUACCT) += cpuacct.o

obj-$(CONFIG_CPU_FREQ_GOV_SCHED) += cpufreq_sched.o

kernel/sched/tune.c

0 → 100644
+16 −0
Original line number Diff line number Diff line 
#include "sched.h"



unsigned int sysctl_sched_cfs_boost __read_mostly;



int

sysctl_sched_cfs_boost_handler(struct ctl_table *table, int write,

			       void __user *buffer, size_t *lenp,

			       loff_t *ppos)

{

	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);



	if (ret || !write)

		return ret;



	return 0;

}

kernel/sysctl.c

+11 −0
Original line number Diff line number Diff line
@@ -434,6 +434,17 @@ static struct ctl_table kern_table[] = { 
		.extra1		= &one,

	},

#endif

#ifdef CONFIG_SCHED_TUNE

	{

		.procname	= "sched_cfs_boost",

		.data		= &sysctl_sched_cfs_boost,

		.maxlen		= sizeof(sysctl_sched_cfs_boost),

		.mode		= 0644,

		.proc_handler	= &sysctl_sched_cfs_boost_handler,

		.extra1		= &zero,

		.extra2		= &one_hundred,

	},

#endif

#ifdef CONFIG_PROVE_LOCKING

	{

		.procname	= "prove_locking",